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61.
Edwards HG Herschy B Page K Munshi T Scowen IJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):191-195
The aim of this work is to investigate the viability and potential of three groups of organic compounds as biomarkers in a future robotic analytical exploration of Mars. The three compounds have been identified as suitable candidates for potential biomarkers for extant or extinct life from the terrestrial fossil record. The three groups of compound were all similar in structure, being either tetra- or penta-cyclic compounds. The limits of detection for a sample were also tested to estimate what concentrations it would still be amenable to Raman spectroscopic investigation. This was investigated using both solid mixtures and liquid solutions. The spectra of these compounds are characterised so that they can be added to the Raman database for future Mars missions. This involved identifying functional group characteristics, assigning peaks for each individual sample and characteristic features which would categorise the samples. 相似文献
62.
Extensive studies have been carried out on the optical conversion of F and F-aggregate colour centres produced in lithium
fluoride single crystal on gamma irradiation. Using 308 nm XeCl laser it has been shown that significantly large population
build-up of F
3
+
centre and reduction in the population of undesirable F2 centres can be achieved in gamma irradiated crystal at room temperature due to multistep photoionization processes. These
and other investigations have provided a scheme for possible laser action based on F
3
+
colour centres in LiF crystal at room temperature. 相似文献
63.
64.
Philip C. Bulman Page Genna A. Parkes Harry Heaney J. Steven Wailes 《Tetrahedron letters》2008,49(49):6951-6954
A number of oxazolidines derived from ketones and aminoalcohols have been prepared in excellent yields using microwave irradiation. In most cases, conventional reflux failed to provide any of the desired products. 相似文献
65.
It is shown how the invariance of the Born—Oppenheimer potential energy to overall translations and rotations of a molecule can be used to reduce the computational labor required for derivative evaluations at various orders. 相似文献
66.
67.
Numerical solutions have been obtained for the exact equations describing the propagation of periodic axisymmetric waves in a rigid cylindrical tube. Results were obtained for air over a range of conditions corresponding to shear wave numbers (s = R √?ω/μ) from 0·2 to 5000 and reduced frequencies (k = ωR/a) from 0·01 to 6. For conciseness and convenient application, the results for the attenuation and phase shift coefficients are given in the form of simple polynomials for the ranges 5 ? s ? 5000 and 0·01 ? k ? 6. This range covers virtually all values of tube diameter and sound frequency likely to be met in practical situations that are consistent with a continuum gas model. 相似文献
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